This invention relates to automated parts feeding systems. More specifically, this invention relates to a mobile robot feeding platform with an alternating parts feeding system.
Modern assembly lines are faced with the need to automate more processes, reduce change-over time, spread the cost of capital equipment over more products and cut operating costs. To meet these goals, assembly line operators are turning toward increased equipment flexibility. Vision-guided robotics systems are used to increase the flexibility of assembly line systems. Traditional parts feeding systems are not as flexible as these vision-guided robotic assembly systems. The use of traditional feeding devices, including vibratory bowls, centrifugal bowls and brushes have not been satisfactory for the unique needs of flexible feeding.
During assembly processes, components are typically held in bulk storage. Parts feeders are used to provide manageable numbers of parts from bulk storage to automated processing equipment such as robotic arms and vision systems. Common feeders known in the art are dedicated or semi-dedicated feeders, such as centrifugal or vibratory bowls. These dedicated feeders are more feasible for long production runs and for lines with faster assembly rates, where change-over time and costs are not high priority. Dedicated feeders for small, multiple runs, where flexibility is important, are thus a less attractive solution in assembly line systems. Multiple, dedicated vibratory feeders have been used if feeding of multiple products is needed and the parts themselves do not change. Drawbacks to dedicated feeders are that they are noisy, they take up a great deal of space, and they are not flexible, e.g., mobile or capable of handling a variety of parts.
Intermediate, organized storage containers have also been used to feed parts. These containers are used for banding, blistering and traying of components, but they require specialized handling equipment. This increases the work in process and adds costs because of the intermediate packaging of the products in assembly. Storage costs are increased because there is an increased number of containers needed for staging and warehousing components. The cost of loading the storage devices on the front end of the process makes use of the intermediary containers questionable.
When feeding parts, a system must keep parts sufficiently separated so that robotic arms may distinguish parts and make selections. This requires not only physical separation, but also optical separation. Physical separation keeps the parts from touching during robotic selection and optical separation allows the robotic system to visually distinguish one component from another. Edges of the parts to be processed may also need to be distinguishable to allow a robotic system to effectively pick a part. Edge distinction is generally achieved by various lighting schemes for the feeding system. Because of the need to keep parts separated so that an automated processing system can visually and physically identify and select individual parts from a feeding system, feeding systems known in the art tend to be large, complicated, and costly. In this regard conventional feeding systems are illsuited to small companies in need of flexible assembly systems.
Parts feeding systems include a transporting mechanism to move a part from one point to another, into and through an automated system""s operating range. The transporting system is critical to enhance the operability of the robotic and vision systems, thereby, increasing throughput. The transporting surface is generally both the background for the vision-based robotic system as well as the picking surface. The transporting mechanism not only transports parts into the robotic system""s operating range, but also moves unpicked parts away from the area. In this manner, the transporting system is also an integral part of the parts recirculation system. Mechanical conveyors known in the art pose difficulties for vision systems because they don""t generally have a visually uniform surface that facilitates visual separation of parts. Furthermore, small parts may be easily damaged or caught in conventional flat-top chain conveyors because of large gaps in the conveyor surface.
While some prior art belt conveyors have eliminated seams that interfere with vision based robotic systems, they are designed to operate linearly which makes transporting parts around corners difficult. The speed at which the parts are transported to and through the robot""s operating range is directly related to the through-put of the linear belt system. The speed includes the settling time necessary to stabilize components once the transport mechanism has stopped. In a linear belt system there is some period of time in which the system comes to a stop to allow the parts to settle and, therefore, during this time a robotics system is not efficiently selecting parts.
Flexible belt feeders commonly operate in two modes: intermittent and continuous. In the intermittent mode, the feeder is turned on to move components into and out of the operational range of the robotic system. The feeder is then turned off to allow parts to settle and then to allow the robotic system to capture the image and pick the part. In continuous mode, the feeder is always on. The vision system captures the component image upstream of the picking area, and the system tracks the location of the part as it travels to the picking area. The robot arm then picks the part while the component is still moving.
A third, hybrid mode, utilizes a combination of continuous and intermittent modes. For example, one such hybrid mode is to run the feeder continuously until acceptable components are within the vision system""s operating range and then intermittently to pick them.
One limitation with conventional feeder systems is that the cycle time of the feeder must not be more than the time it takes the robotic arm to transport the picked part to a placement area and return to the picking area. Also critical is the time it takes the component to settle and the image system to acquire the component. Therefore, there is always a period of time in which a feeding system must allow parts to settle during which time the robotic arm is inactive.
For a feeder operating in continuous mode, the cycle time is the time between successive presentations of acceptable parts. A limitation of this mode is that acceptably oriented parts may pass through the picking area while the robotic arm is in the placement position or while it is moving to or from the picking area. The cycle time for the feeder is extended until both an acceptable part is present and the robotic arm is capable of picking the acceptable part after it has settled and is separated from other parts.
It is therefore an objective of the present invention to provide a parts feeder for a robotic system which overcomes the shortcomings of the prior art.
It is an objective of the present invention to provide an improved flexible parts feeder that is mobile and has a small footprint.
It is a further objective of the present invention to provide an improved flexible parts feeder that accommodates various automated parts processing system configurations at a relatively low capital cost to a user.
It is yet another objective of the present invention to provide an improved parts feeder for a robotic system in which the cycle time of the system is virtually eliminated and which allows for a robotic system to continually have settled parts from which to choose.
The objectives of the present invention are achieved with a parts feeder for a robotic system in which in one embodiment the parts feeder has a tilting pan as a diverter which receives parts from a feed conveyor to supply parts to return conveyors traveling in a direction opposite to the feed conveyor for alternately returning parts to a hopper. A first conveyor allows a robotic system to pick parts therefrom while a second conveyor returns parts to the hopper and, thereafter, the second return conveyor allows the robotic system to pick parts therefrom while the first return conveyor returns parts to the hopper.
In one aspect of the present invention, a parts feeder has a hopper with an integral hopper conveyor for transporting parts to a chute integral with a frame of the parts feeder. The frame has a second end where parts are received into the chute and then transported by a feed conveyor to a first end of the frame where the parts are presented to a parts diverter. The parts diverter may be comprised of individually actuated gates that push the parts to a desired location of the feeder, or may be any other mechanism suitable for guiding parts. In a preferred embodiment, the parts diverter is a pan that is pivotally attached near the first end of the frame. The parts pan alternatingly dumps parts received from the feed conveyor on to first and second return conveyors located on opposite sides of the parts pan. While the parts pan is dumping parts onto the second return conveyor, the first return conveyor transports parts into an operating range of a robotic arm controlled by a control system to select and pick parts f or desired reorientation.
After a part has been selected and picked by the robotic arm from the first return conveyor, another group of parts received from the feed conveyor into the parts pan is dumped onto the first return conveyor as the first return conveyor simultaneously moves parts not selected by the robotic arm out of the robotic arm operating range. While the first return conveyor is in motion, the second return conveyor locates parts into the robotic arm operating range where the robotic arm selects and picks parts therefrom to be reoriented as desired. The second return conveyor, thereafter, transports the unpicked parts out of the operating range and receives more parts from the parts pan, as described above for the first return conveyor.
Parts not picked by the robotic arm from the first and second return conveyors are recycled into the chute, whereafter they are transported by the feed conveyor back to the parts pan to be once again dumped onto either of the first and second return conveyors. A parts sensor detects the quantity of parts held within the chute to regulate the quantity of parts supplied to the frame by the hopper conveyor.
In another aspect of the invention, the parts feeder may be used with automated visual inspection equipment that is configured to inspect parts positioned within the operating range on the return conveyors.
In yet another aspect of the invention, a mounting plate attached to frame has a plurality of holes which allow a user to attach a shelf at a desired location for mounting a robotic arm, visual inspection equipment and other appropriate components.